When you send a photo to somebody in iOS 12 or earlier, you also share that photo’s location. If you upload a picture to a classified ad or auction site, you potentially show everyone exactly where you live. And if you send a photo to a friend or family member, they may share that image publicly (on Facebook, for instance) — and share your home address along with the picture.
In iOS 13, you can disable location sharing for any photo you share. Some annoying limits hurt this new feature, and you have to remember to do it every time you share an image or video, but it’s still a lot better than what we have in iOS 12.